Adaptive backstepping fast terminal sliding mode control for nonlinear uncertain active suspension system with mechanical elastic wheel

This paper proposes an adaptive backstepping integral exponential fast terminal sliding mode controller (ABIEFTSMC) to stabilize the body attitude of vehicles equipped with new mechanical elastic wheels (MEW) while improving the ride comfort. The controller takes into consideration the nonlinearity and uncertainty of the active suspension system (ASS). First, conduct experiments to determine the vertical mechanical characteristics of MEW. Then, in the controller design, a novel type of integral exponential sliding mode surface is introduced, which demonstrates the stability of the sliding mode dynamics and finite-time convergence. On this basis, the system model is reconstructed, and subsequently, a backstepping integral exponential fast terminal sliding mode controller is designed based on the Lyapunov functions. Considering the existence of uncertain suspension spring and damping forces, an adaptive radial basis function neural network is incorporated to approximate uncertain forces, forming an ABIEFTSMC that can adjust network weights online. The proposed controller combines several advanced control methods, minimizing convergence time, improving transient response, increasing robustness, and reducing chattering. Finally, simulations are performed under different types of disturbance inputs to validate the effectiveness of the proposed controller. This research advances SMC technology for nonlinear uncertain ASS and expands the application scope of MEW.